The relationship between vessel traffic and noise levels received by killer whales and an evaluation of compliance with vessel regulations
MetadataShow full item record
Whale watching has become increasingly popular as an ecotourism activity around the globe and is beneficial for environmental education and local economies. Southern Resident killer whales (Orcinus orca) comprise an endangered population that is frequently observed by a large whale watching fleet in the inland waters of Washington state and British Columbia. One of the factors identified as a risk to recovery for the population is the effect of vessels and associated noise. Federal regulations limit the approach distance of vessels to 200 m and voluntary guidelines suggest a maximum vessel speed of 7 knots within 400 m of the whales. An examination of the effects of vessels and associated noise on whale behavior utilized novel equipment to address limitations of previous studies. Digital acoustic recording tags measured the noise levels the tagged whales received while laser positioning systems allowed collection of geo-referenced data for tagged whales and all vessels within 1000 m. The objectives of the current study were 1) to compare vessel data and DTAG recordings to relate vessel traffic to the ambient noise tagged whales receive and 2) to utilize the vessel data to examine vessel behavior during whale watching and assess trends in vessel behavior over time. Vessel attributes found to be significant predictors of noise levels in the likelihood model, using all intervals of vessel and noise data, were length (inverse relationship), number of propellers, and vessel speed (however, R2 = 0.15). When intervals that only recorded the research vessel were excluded, the only significant predictor of noise levels in the likelihood model was vessel speed (R2 = 0.42). Average vessel speed and number of propellers per interval were the only significant correlates with noise levels using simple linear regression (i.e. ignoring other concurrent characteristics). Research, commercial whale watching, and private whale watching vessels increased their distance from observed whales over time. The occurrence of research and commercial whale watching vessels within 100 m of a tagged whale also significantly decreased over time. However, vessel speed (excluding research vessels) significantly increased over time for vessels at distances of 200 m and 400 m from whales. Compliance with the distance regulation has improved, even though distance was not a significant correlate with noise levels received by whales. Increases in vessel speed are a cause for concern since speed was the most important predictor of noise levels received by whales in this study. The information presented here may be useful to managers in assessing the effectiveness of current recovery efforts.
- Fisheries